Methods for measuring ripple and noise

The best method is "tip and ring"  to measure directly across the input or output capacitor.  That way the ground loop is minimized.  If you need additional assistance, there are reference materials on the web if you search.  If you cannot find them, I do have them down load and can forward tehm, but it will be tomorrow when I get back to the office.   Post a follow up if you need them.

thanks,

I find several material..... but I cant understand if there is standard or not....if good limit BW at 20 Mhz or not...or there is good BW for each switching frequency

you are very kindly if you can send me your material or your standard

Thanks

If you are looking just to see the actual ripple voltage, then 20 MHz BW will suffice.  the fundamental ripple component will be at the switching frequency which will be much less than 20 Mhz.  If you are concerned about noise, you may want to increase the BW.   Ringing from over or undershoot of the switching node may have frequency components in the  30 - 150 MHz range.  You have to be careful when measuring as any amount of loop in your probe and ground path can pick up stray radiated energy and cause your waveform to look worse than it actually is.  I'll post some reference material later when I get into the office.

excuse me

When are you free, please send me some material.

thanks

Here is a "power tip" from our archive...8712.power_tips_6.pptx